The present invention relates to a filter device for filtration of fluids, in particular with extraction of a filtered sample fluid from containers and tube conduits for measuring purposes.
In known filters of this type the sample fluid is extracted from containers and tube conduits for measuring purposes and after the measurement is rejected. This has the disadvantage that the sample fluid is lost. Further disadvantages of known filter devices resides in that, for cleaning purposes a larger throughput of sample fluid and a greater expense for the sample preparation is required, and the installation cost is high. Other filter devices have the disadvantage of a low filtering rate or of an uncomplete exchange of the sample fluid given a change of the sample fluids. Often a sterile operation is only possible with high apparatus expense.
Accordingly, it is the object of the invention to provide a filter device with which a sterile handling of the sample fluid is possible with a low cost with regard to an apparatus.
In keeping with these objects, one feature of the present invention resides, briefly stated, in filter device which has a closed fluid circuit including at least one first filter element, a fluid pump, a second filter element arranged so that a sample fluid is suctioned via said first filter element out of a container or tube conduit and via said second filter element is pumped back into the container or tube conduit, or vice versa.
The filter device according to the invention has the advantage that during the measurements no sample fluid is used up, since it is continuously led back again in a closed fluid circuit into the container or the tube conduit from which it was taken. The filter elements keep back dirt particles and in particular bacteria, and thus ensure a sterile sample fluid. Since the closed fluid circuit is provided, the sample fluid also in the further course is not contaminated by the filter system.
In accordance with another feature of the invention the pump direction is reversible. By reversing of the pump direction a cleaning effect may be achieved, since the particles and bacteria filtered out for example by the first filter during the original pump direction and clinging to this first filter, are flushed away with the reversed pump direction and the first filter is thus cleaned. Thereby the servicable duration of the filter device is advantageously increased, in particular when the reversal procedure is repeated at several time intervals.
In accordance with a further inventive feature, the device is further improved in that, the pump direction is automatically reversible, preferably periodically. This construction spares the manual switch-over of the pump and ensures a long trouble-free operation since the switch-over may thus no longer be forgotten.
It is further feature of the invention that the filter elements are exchangeable and thereby the filter fineness and the volume flow through the filter device can be adjusted by exchanging variously designed filter elements. The filter device can be thus advantageously adapted to the various requirements of the measuring operation without great expense.
In a preferred embodiment of the invention, the device elements are mounted on a common assembly carrier. As a result a compact construction of the filter device is provided, which needs only a little sample fluid, is flexible and permits further advantageous design forms.
In a particularly simple, inexpensive and useful embodiment of the invention, the assembly carrier can designed as a carrier tube. A probe flange, a process flange, a first tubular filter element, a separating ring or O-ring, a second tubular filter element and a closure screw screwed into the tube end can be arranged on the carrier tube. This provides the advantage that the components are manufactured with little expense, are easy to keep clean and can be assembled in a simple manner, in the specified sequence. They are simply stuck on the carrier tube and rigidly connected to one another by a closure. Furthermore the tubular formation of the filter elements has the advantage of a relatively large filter surface which permits a large volume throughput.
A further advantage of this construction resides in that the components may be easily exchanged, and specifically not only when a replacement is needed. In particular the filter elements here can be exchanged for other filter elements with other properties, for example with a different filter fineness and a different volume flow, if a greater or lesser throughput of the sample fluid is desired.
The separating ring can be provided for preventing a direct spilling over of a sample fluid from the inflow region into the outflow region. This is achieved by sealing from one another of the two annular spaces arranged radially within the tubular filter elements, and also by sealing the end faces of the filter elements, so that here no fluid can exit. For this purpose the separating ring is designed relatively complex and consists, for example, of a profiled metal ring which is provided with four O-ring seals. If however filter elements are used with a sealing of the end faces due to the construction type, the separating ring can be replaced by a simple O-ring which now only needs to seal the two mentioned annular spaces from one another.
The connection of fluid conduits to the pump and back is simplified in the inventive device, in that the probe flange and the process flange are each provided with a connection bore for the inflow and outflow of sample fluid.
Advantageously a measuring arrangement is integrated within the filter device. This feature uses the fact that the fluid flow within the filter device is accessible without additional expense with regard to apparatus. By way of saving of diversions of the measuring arrangement, the total quantity of circulating sample fluid is advantageously small.
In accordance with the invention, it is recommended for the measuring arrangement to include an optical probe. Therefore, by probes many properties of the sample fluid may be determined without chemically changing it.
The inventive filter device can be narrowed when according to the invention a measuring probe is arranged within the carrier tube. Thus the installation space which is available here can be efficiently used.
The optical probe can have an essentially cylindrical shape, and its free end arranged in the region of the closure screw can be provided with a spacer sleeve. The probe can be centered in the carrier tube and fixed in a defined position, which is particularly advantageous with optical measurements. Therefore, the dead space within the carrier tube and the total circulating fluid quantity can be also reduced.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.